Boiler



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F. B. HOWELL BOILER Amm 2, m9.

.N .WON

Filed April e, 1925 Amm 2, w29.

F. B. HOWELL BOILEH Filed April 6, 1925 5 Sheets-Sheet 2 pr Z, w29.

F. B. HOWELL LQS.

BOILER 5 sheets-sheet 5 Filed April 6. 1925 uit@ a April! 2, i929., F.B. HOWELL BOILER 5 Sheets-Sheet 4 Filed Aprillh.

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5 Sheets-Sheet BOILER F. BT. HOWELL Filedl April e, 1925 Wmv a serbaFRANK B. H/VEL, F BUFFALG, .NEVI "ERK, ASSIGNOR TO AIVLERICAN RADIATORCOMEANY, OF IJ YGRK, El. Y., il. CRPORATIGN OI NEN JERSEY.

BOILER.

Application led April 6,

My invention relates to improvements in heating apparatus and the samehas for its object more particularly to provide a boiler for heatingpurposes in which the fuel will be consumed etiieiently and smokelessly.

Further, said invention has for its object to provide a boiler having alarge mass of highly heated material disposed in and about thecombustion chamber whereby te maintain a temperature above the ignitionpoint of conibustible gases prior to and during 'the time the saine arebeing supplied with preheated secondary air to insure the perfect andcomplete combustion of said gases.

Further, said invention has for its object to provide a boiler in whichsecondary air is supplied to the products of combustion at the rear ofthe fuel receptacle and, in which, prior to its combination with theproducts of combustion7 the air is preheated by exposure to the heatradiated and conducted to the same from the incandescent fuel in saidreceptacle.

Further, to provide said invention has for its object a boiler in whichthe means for supplying secondary air serves as the rear wall of thefucl receptacle, am` is exposed to the heat of the incandescent fuelupon the grate.

l FurtherU said invention has for its object to provide a boiler inwhich the means for supplying secondary air, which means foi-nis theroar wall of the fncl receptacle, is formed of a plurality of parts orsections whereby to permit of the ready removal of parts which maybecome damaged by ci-;posure to heat. and to permit of the substitutionof new parts therefor.

Further, said invention has for its object te provide a. sectional wallof the type specilic-il in which the parts vthereof are indcpend fitlymounted toA permit the individual rein eval thereof7 and in which thesaine are arranged edge to edge to provi. le a substantially continuousrear wall for the fuel receptacle.

Further, said invention has for its object to provide a boiler in whichthe secondary air is supplied to the products of combustion in a seriesof jets extending entirely across the boiler at the rear of the fuelreceptacle.

Further7 said invention has for its object to provide a boiler in whichsecondary air, in a highly heated condition, is supplied to the productsof combustion as the same pass towards the flue and the mixture then di-1925. Serial No. 21,118.

rected towards a facing oi heat absorbing material whereby to maintainVthe temperature thereofsulliciently high to insure complete combustion.

Further, said invention has for its object to provide a boiler havingmeans affording convenient access thereto to permit of the replacing ofsuch parts of the superimposed rowsa forming a facing of heat absorbingmaterialj may become burned rout or otherwise damaged in the course ofoperation.

Other objects will. in part be obvious and in part be pointed outhereinafter.

To the attainment of the aforesaid objects and ends my inventionconsists in the novel fe tures of construction, and in the combination,connection and arrangement of parts hereinafter more fully described andthen pointed out in the claims.

ln the accompanying' drawings forming part of this specification- Figurel is a side elevation with parts broken away and with parts in section.showing one form of boiler constructed according to and embodying mysaid invention;

Fig. 2 is a front elevation of bridgewall sections thereof, a centergrate support being shown in section;

Fig. 8 is a partial sectional view thereof on the line 3 3 of Fig. 2,looking in the direction of the arrow;

Fig. l is a sectional view on the line 4 4 of Fig. 2 looking in thedirection of the arrow;

Fig. 5 is a sectional view similar to that of Fig. lJ with the partsthereof disassembled;

Fig. G is a sectional plan view of the parts illustrated in Figs. 4 and5;

Fig. 7 is a. perspective view of a plate or member employed for formingthe secondaryair supplying means;

Fig. 8 is a side elevation of a portion of the boiler showing` means forpern'iitting access to th-e interior thereof;

Fi 9 is a front elevation of portions ofthe baille sections of theboiler, with parts in seetion, and showing a facing of heat absorbingmaterial thereon and means for permitting access thereto;

Fig. 10 is a sectional view thereof on the ine lO-l() of Fig. 9. lookingin the direction of the arrow;

llig. ll is a front elevation of the rear seetions with parts insection, and showing a facing of heat absorbing material thereon,

and means tor pe'rn'iitting access thereto, and

F i g. l2 is a partial sectional view thereof on the line 12-12 of Fig.ll, looking in the direction of the arrow.

Referring to the drawings the boiler is shown as coniprising separatehalves and 2l arranged laterally side by side, and each composed of aplurality of hollow sections including a 'front section 22, a backsection 23, and a plurality et intermediate sections 2li.

rllhe intermediate sections 2li andthe bri d gewall sections compriseouter lower vertical portions 2G 'forming the side walls o't the boiler,and inwardly extending upper portions 27 'torn'iing the top oit theboiler, corresponding sections ol the haltl parts 2O and 2l beingarranged adjacent to each other and enclosing the eon'ibustion chamberQ8, fuel receptacle Q9, 'llues 30 and ash pit 3l. l.)

The portions'QG of the several sections 2?), 24 and 25 of each part orhalt Q0 or 2l of the boiler are provided with registering or alinedopenings 3Q in which are disposed the usual nipples (as sho 'n at theupper portion ot Fig. l) whereby the several sections maintained inassembled reladionv an d in comn'iunication with each otlie to providetree circulation oit Vfluid through the b iler:

ln like manner the upper portions 27 et mich set o'lE sections areprovided with alined or registering openings (Fig. l) and secured bynipples A manifold 34 l) is secured at its opposite ends to the upperportions oit the i back sections 23, and has a single `flow core nectionor outlet intermediate its ends. The lower portions of said backsections Q3 are similarly connected by a maniitold 3G which has areturi'i .flow connection or niember 37.

At a suitable point intermediate the front and back sections areprovided registering intcrn'lediate sections 25 having inwardlyextending hollow vertical members 38 forming bridgewalls communicatingat the outer ends thereof with the vertical portions Q6 ot said internediate sections 25, and having integral hollow risers 39 at the .innercontiguous endscommunicating with the upper portions`27 oit theintermediate sections 2f. rlhe bridgewalls 38 together with the frontsections QQ and side members 26 'term the tuel receptacle 29 and ash pit3l.

Grate bars 4:0 (Fig. l) which are arranged i in sets upon opposite sidesof the boiler are supported at their outer ends on the sections 2G whichterm the longitudinal. or side walls of the boiler, and at their innerends upon opposite sides et a common water bacli'ed central gratesupport 4:1 Fig. 2) mounted between. and upon the 'liront sections 22and bridgewalls 38. The grate bars 40 ot each set or halt ot the boilersections 20, 2l are movably mountedn and are provided willi downwardlyextending arms l2 connected 'to Lacasse bars 43 whose -forward endsextend through the lront sections and are secured to levers 44 adaptedto be engaged by a shaker bar whereby said grates may be actuated.

rllhe boiler is enclosed by a jacket l5 of heat 'insulating material andis provided at the front with the usual tire doors 46, and ash pit doors47 having openings 1:8 having regnlating slides for controlling theadmission oli air.

Mounted upon the lront upper portion ot the vertical brido'ewalls 38 ismeans t9 for supplying secondary air to the products otl combustion inthe combustion chamber 28 as the same enter the tlues through openingsor outlets 5() above the bridgewalls 38, the openings 5() beingsubstantially coextensive in length with the width of the fuelreceptacle.

Means 4) comprises an auxiliary vertical. wall or member 5l constitutingthe rear wall et the fuel receptacle and spaced from the bridgewalls 3Sto n'ovide between the same a vertical opening or openings 52. Said member 5l terminates at its lower edge 53 slightly below and behind thegrate bars 40, whereby each opening 52 is in communication with the ashpit at one end 54tand with the combustion chamber 28 at its opposite end55.

'lhe member or members 51 (the member being in parts arranged uponopposite sides ot the central grate support ll and risers 39) arepreferably sectional, comprising sectional members or plates 5Garranged. to provide a. continuous wall, and, as illustiated7 edge toedge.

rYlhe plates or members 5G are independently and detachably mounted uponthe bridgw walls 38 to permit the individual removal thereof as the samebecome damageda and also to permit independent expansions thereot toprevent warpiiig. A

For this purpose the fronts oit the water backed bridgewalls 38 areprovided with. ver tical water backed supporting members or brackets 57projecting outwardly therefrom and arranged in spaced relation along`the said bridgcwalls 38. Each supporting member 57 comprises laterallyprojecting Pplate retaining` members or flanges at the tor ward portionsot the same arranged in parah lelism with the bridgewalls. The retainingmembers or flanges 58 have notches 59 therein intern'iediatc their npperand lower ends, and siuniortinel devices or ledges 59a behind. the samebelow said notches 59 to support plates 5G.

Each plate 5G 4 to 7) is provii'led with a il'urality ot' verticallyarranged ribs G0 upon its inner surface, the outer oit the ribs havingupper and lower sets ot spaced lugs 6l constituting n'ieans tor mountingthe plates upon the lugs 59 of the brackets 57 behind the members 58.rl`he lugs (Si are so located en each plate as to permit the plates 56to be inserted between adjacent members 57 withthe ribs 50 thereotloccupying' the spaces between flanges 58 (see Fig. 3), the upper set otlugs 61 being passed over the top et the 'flanges 58 and the lower setolugs 61 through the notches 59 thereo't. The plates 56 are then loweredor permitted to drop, the lower lugs (il engaging the ledges 09a,thereby snpiliorting thel plates in position with the lugs (Sl thereonpositioned behind the retaining members 58.

Means is also provided tor detlecting the secondary air rearwardly asthe same enters the con'ibustion chamber 28. This means is 'termed byconstructing the upper end of each plate with an upwardly and rearwardlydirected angular portion G2 whereby the vertical opening 52 at the upperend 55 thcreot is constricted, said angular' portion G2 at 'the innerside having rib portions GO constituting upper continuations ot the ribsG0.

The ribs (SO. (30 not only serve to strengthen the plates 5G but alsoprovide means or channels tor increasing the metal surface-in contactwith the secondary air to more etliciently heat the same.

rllhe opening is divido'l in to vertical passages or channels G3 by fl l'ackets 57 to torni means tor dividing the secondary air to supply thesame in jets to the products ot con'ibustiou. As shown more clearly in2l Vhe rib portions G a also further divide the upper end ot the opening52 to provide a plurality oit constricted pa sages or outlets (il torsupp the secondary air in jets to the products ot combustion.. Thepassages G8, 'el formed by the brackets 57 and ribs GO are arrangedsubstantially coextensive with the width ot the Ytuel receptacleinsuring the supply ot a maximum quantity ot secondary air in to theproducts ot combustion, while peiniitting` the renioval a d replacementet the plates 5G, should the saine become damaged.

The products ot combustion combined with the rearwardly deliectcdsecondary air iinpinoje, in passing through tho openings 50, upon hollowbattles l, 9 and 10) comn'iunicating at 'the outer ends thereof with thevertical portions 26 ot a pair oi contiguous intermediate sections 24,and communicating at their inner contiguous ends with the portions 27 otthe same sections throiiigh integral hollow risers 6G.

The fronts ot bullies 65 are provided with farines G7 ot heat absorbingand retaining` material against which the gases or products o tcombustion impinge and which insure coin-- plete combustion thereof bythe n'iaintenanee ot a hi gh temperature thereby in the vicinity ot thecombustion chamber 28 where the secondary air combines with theproduct-s of con'ibustion.

In like manner the bottom or tioor of the flue 30 is provided with afacing 68 ot heat absorbing and retaining material which the products ofcombustion pass as the same sweep downwardly between the bridgewalls 38and baflies 65. The products of combustion are then directed upwardlybetween the battles G5 and the water backed rear sections 23 which havefacings 69 ot heat absorbing material thereon. The provision of theseveral heat retaining suritaces 67, 68 and G9 within the tlues 30maintains theinterior thereof at a sufticiently high temperature toinsure complete combustion ot the gases before the same enter thegalleries 7G and pass outat the rear thereof through the outlet 7l tothe chimney.

The tacings 67 on the battles G5 preferably comprise a row ot blocks orbrick 67L mounted in horizontal guideways or supports 72 formed in thebatlles. rlhe guideways 72 include spaced horizontal ledges or retainingmembers 73 between which and in which the blocl 67a are supported andretained, said ledges converging towards each other at the fronts. Theledges 7 fl of the battles 65, are alined or re0 ster at their innerends 7 4t, torming a substantially continuous guideway, and are open attheir outer ends 75 to permit the removal there'trom or the insertiontherein of blocks tln'ough openings 76 in the side portions of thebaille sections 24 and iacket- 45.

As shown in Figs. 9 and 1t), the openings 7 G at opposite sides ot theboilers are surrounded by trames 77 having flanges 78 inserted along`the edges of the openings 76, and secured against the jacket l5 by meansot bolts 79 extending through the jacket Ll5 and secured in openings orholes 8O in the battle sections 2st. The openings 8() are backed by acup. shape partition 8l to prevent leakage. The opening through each'trame 7 7 is closed by a removable cover 82 secured to the trame byrotatable locking bolts 83. rllhe bolts 8? have fingers 84 at theirinner ends adapted to engage behind ledges 85 on the trames 77, andhandles 86 at their outer ends whereby the bolts 83 may be rotated todisengage the ledges 85 and to remove the covers 82. The guideways 72are also provided with horizontal ribs 87 to space the blocks 67 fromthe battles G5 to reduce the rate ot conduction of heat from the blocks67"L to the balli-es 65 which, being water backed, would tend otherwiseto cool said blocks.

The tacings 69 (Figs. l, 8, l1 and 12) upon the rear sections 23comprise a plurality ot. horizontal rows 88 of blocks or brick G9 ofheat. absorbing material. The rows 88 are in depen dently mounted insuperimposed horizontal guideways or supoorts y89 formed on the 'frontsof the rearsections 28. The supports 89 comprise horizontal top andbottom brick or block retaining flanges or ledges 90 and intermediateledges or tianges 91 parallel therewith, whereby the rows 88Yareindependently supported between adjacent flanges in spaced relation toeach other.

The inner ends of the several flanges 90, 91 on the sections 28 arealined or register, ttorming substantially continuous guideways trom f by bolts T9 secured to the section side to side of the boiler and theouter ends 92 are open to permit 'the removal and insertion o'1 theblocks (35) through openings 93 in opposite sides oit the boiler7 whichopenin are common lo the plin'aliiy oi rows 8S at opposite endsthereoii.

lhe openings 93 are surrounded by trames 77 (similar to the iframes '57previously described) common to the plurality oit' rows 88 at oppositeends. lilach traine 77' is secured against the iaclret iand a rearsection /ll The openings ,in said iframes lll are norn'ially closed byvthe covers S2 common to the several rows at opposite ends thereof.y thecovers being secured in place by locking bolts 8f3 constructed andarranged as previously described in connection with the bolts d?) shownin .i 9 and 10. 'llheguidoways tlf) are likewise 5 rovided with ribs 87to space 'the blocks-(3STL1 from the water backed rear section toprevent the too rapid conduction of heat absorlmd by said blocks to thecooler section Q3.

ln operation the air is supplied 'from Yhe ash pit 3l upwardly throughthe gra es 4l() to the iuel thereon causing theA same to burn. Thepartially consumed products otcombustion or gases thus :termed passrearwardly (as indicated by the arrows l) towards the openings 50 wheresecondary air is supplied thereto to combine therewith to insurecomplete combustion. The secondary air is also supplied trom the ash pitthrough the openings 52 at the rear oit the 'fuel receptacle 29. lnpassing through the opening 52 the secondary air, which is directlyexposed to the heat ot incandescent fuel in the receptacle 29, becomespreheated. said air being in contact with the relatively large metalsurtaces consisting ofi the plates 56 with the ribs 60 thereon whichdirectly receive said heat by conduction and radiation from theincandescent fuel. rlhe preheated. secondary air passing through thepassages Atermed by the ribs 60a and brackets 5'? escapes in jets fromthe openings 641-. and combines in the chamber 28 with the partiallyconsumed products oli combustion, said permitting maximum contact andcombination thereof with the prod.- ucts oi combustion. The products oicombustion then pass rearwardly and npinge on Athe tacin 6i' of heatabsorbing material, 'the latter absorbing and retaining` heat lthereinto maintain the adjacent portions of the boiler at a high temperature toinsure com plete com bustion. As the products ol combustion pass intothe iiues 30 the :tacings G8 and G9 are highly heated, the heat beingretained thereby to maintain the interior o'i the flues at a maximumtemperaturej thereby causing complete combustion and maintaining theproducts 0l. combustion passing the same at a ifi/eases maximumtemperature so that the water circulating in the portions 27 of theboilers about the galleries will be eiiiciently heated as such highlyheated products of combustion pass therethrough. The quantity ofsecondary air supplied to the products et combustion is automaticallycontrolled by the rate of combustion.

Should any et' the plates 56 become cracked or broken the same may beeasily removed and a new one inserted in place as above described.

ln case any of the blocks G7, 69 become broken or cracked and fall intoflue portion 30, the closure or closures 82 or 82a are unllocked andremoved7 the blocks remaining in place are moved along` by a suitableinstrument or tool inserted through the opening, to lill up the spaceslett by the blocks which have dropped out, and new blocks are insertedthrough the opening to complete the row. rlfhe closure oi' closures arethen replaced to maintain. the side walls air tight or to prevent theescape et the products oi combustion therethrough. lly independentlymounting the rows 88 any block in one row may be readily removed andreplaced without disturbing any et the other rows.

lThe secondary air supplying` means 49 embodying my said inventionprovides a construction which is simple, and readily and convenientlyarranged in the boiler. The saine is positioned to be exposed to theheat oi the incandescent iuel in the fuel receptacle, thereby insuring amaximum preheating of the secondary air iior combination with theproducts oi" combustion.

rlhe sectional wall and the independent mounting et the constituentparts thereof permits unequal. expansion oi said parts due to heatwithout distortion or warping thereof and the individual replacement o'fsaid parts.

Further, a sectional rear wall for the fuel receptacle is provided whichis substantially continuous and which with the bridge wall forms anopening therebetween 'for feeding air 'to the products of combustion atpoints substantially coextensive with the width of the luel receptacle.

Further, the preheated air combines with the products oi combustion .inthe vicinity of facings et heat absorbing and retaining material whichmaintain the ilues at a suilieiently high temperature to cause completecombustion and to insure the delivery oit the gases at such hightemperature to heat the water circulating in the boiler.

lly my invention a boiler is provided which is substantially smokelessand which will burn sott coal with the greatest economy.

Having thus described my said invention7 what l claim and desire tosecure by Letters Patent isl. A boiler comprising a water backedtransverse vertical wall, a sectional member arranged in parallelismwith said wall, and

coertensive in area with the portion thereof extending above the grate,and means including water backed members on said wall for detachablyengaging and supporting the elements of said sectional memberseparately; said sectional member being spaced with respect to said walland having its lower edge wholly free thereof to provide means for thevertical passage of secondary air therebetween to the products ofcombustion, substantially as specified.

2. A boiler comprising a fuel recepta-c e, a transverse vertical wall atthe rear of said fuel receptacle, and a plurality of plates severallydetachably secured to the front of said wall and constituting theunbroken rear wall of said fuel receptacle; said first named wall andsaid plates being` spaced relative to each other to provide means forthe passage of secondary air vtherebetween to the products ofcombustion, and said plates having their upper ends inclined rearwardlyto form jointly a deflector, substantially as specified.

3. A boiler comprising a transverse vertical wall, a member composed ofa plurality of plates, means on said wall for severally securing saidplates on said wall and in spaced relation thereto with their loweredges wholly free thereof and constituting therewith means for thepassage of secondary air to the products of combustion, and means fordividing said air into a plurality of ets, substantially as specified.

4. A boiler comprising` a transverse vertical wall, a series of separateplates det-achably secured to said wall in spaced relation theretoy andconstituting therewith means for the passage of secondary airtherebetween, and means dividing the space between said plates and saidwall into a plurality of vertical passages for feeding said air in etsto the products of combustion as the same pass over said wall, and meansalong the upper edge of said series of plates for deflecting thesecondary air rearwardly over said transverse vertical wall,substantially as specified.

5. A boiler comprising a transverse vertical wall, a member arranged atone side of said wall, and means for mounting said member in spacedrelation to said wall; said means forming a plurality of verticalpassages between said wall and member for the passage of secondary airto the products of combust-ion, substantially as specified.

G. A boiler comprising a transverse vertical wall, a sectional memberarranged at one side of said wall, and means for detachably mountingsaid member on said wall in spaced relation thereto; said means forminga plurality of vertical passages between said wall and said member forthe passage of secondary air therethrough to the products of combustion,substantially as specified.

7. A boiler comprising a transverse vertical wall and a parallel memberarranged at one side thereof in spaced relation thereto; said wall andmeinberhaving its top curved rearwardly, and terminating in a planeabove sa id wall te form a censt-ricted opening therebetween for thepassage of secondary air therethrough to the products of combustion, andmeans arranged upon the back of said member dividing the space to therear of said member into a plurality of air passages, substantially asspecilied.

8. A boiler comprising a transverse vertical wall, a plurality of plateshaving angularly arranged ends, vertical ribs on said plates, and meansfor .detachably securing said plates separately to said wall in spacedrelation thereto; said angular-ly arranged ends and the upper edges ofsaid wall Jforming a constricted opening therebetween substantiallycoextensive with the width of said wall, and said ribs and said securingmeans forming vertical passages between said plates and said wall forthe passage of said air in jets through said opening to the products ofcombustion, substantially as specified.

9. A boiler comprising a fuel receptacle, a wall at the rear thereof, aplurality of plates detachably mounted upon the front of said wall andforming the rear wall of said fuel receptacle; said plates and iirstnamed wall being spaced to provide a vertical opening therebetweensubstantially coextensive with said fuel receptacle for the passage ofsecondary air therethrough to the products of combustion, and meansintermediate said wall and said plates for dividing said opening intopassages for separating said air into jets, subsmntially as specified.

10. A boiler comprising a fuel receptacle, a water backed wall at therear thereof, a plurality of plates detachably mounted upon the front ofsaid wall and forming the rear wall of said fuel receptacle; said platesand first named wall being spaced to provide a vertical openingtherebetween for the passage of secondary air therethrough to theproducts of combustion, the upper portions of said plates being directedrearwardly to const-riet said opening', and ribs thereon to form aplurality of passages to separate said secondary air into ets,substantially as specilied.

il. A boiler comprising a fuel receptacle, an outlet for the products ofcombustion at the rear thereof, a transverse vertical wall at the rearof said fuel receptacle, and a series of separate members mounted infront of said wall in spaced relation thereto and forming the rear ofsaid fuel receptacle; each of said separate members having its upper enddirected rearwardly to said outlet whereby to deliect tho secondary airpassing upwardly between said member and said wall, substantially asspecified.

12. A boiler comprisin a transverse waterbaclied vertical wall, aplurality of spaced supporting members arranged along said Wall, and aplurality of members independently mounted on said supporting membersand parallel with said wall and forming therewith a continuousin'iperforate wall having a rearwardly inclined upper edge forming adeliector; said in'iperforate wall constituting the entire rear wall ofthe fuel receptacle, substantially as specified.

13. A boiler comprising a fuel receptacle, a transverse verticalwater-backed bridge wall at the rear thereof', an outlet at the rear ofsaid receptacle above said bridge wall, a sectional wall member locatedin frontof said bridge wall and forn'iino' the rear wall of said fuelreceptacle; said bri oe wall and said sec- C tional wall member beingspaced relative to each other to provide therebetween means for thepassage of secondary air upwardly therethrough to combine with theproducts of combustion entering said outlet, means at the top of saidsectional wall member for directing said secondary air rearwardly, and awaterbacked baille' having a facing of heat absorl ing materialassociated with said bridge-wall and spaced rearwardly thereof in thepath of said products of combustion, substantially as speciiied.

11i. A boiler comprising a fuel receptacle, a water backed wall at therear of said fuel receptacle, an outlet at the rear of said ceptacleabove said wall, a water backed baiile spaced rearwardly of said outlet,a facing of heat absorbing material on the front thereof, a plurality ofplates detachably mounted upon the front of said wall and forming therear wall of said fuel. receptacle; said plates and wall being spaced toprovide means for the passage of secondary air upwardly therebetween tothe products of con/ibustion entering said outlet; said means beingsubstantially coextensive with said fuel receptacle, means for dividingthe space between said plates and said walls into a plurality ofvcrtical passages to feed said air in jets, and means for directing saidjets towards said facing, substantially as specified.

l5. A boiler comprising a water-backed bridgevall, an outlet thereabove,a water backed baffle spaced rearwardly of said outlet, a water backedrear wall, facings of heat absorbing material upon the fronts of saidbaffle and of said rear wall, and a plurality of plates detachablymounted upon the front of said bridgewall and constituting the rear wallof the -fuel receptacle; said plates and bridgewall being spaced toprovide means for the passage` of secondary air upwardly thorebetween tothe products of combustion entering said outlet, substantially asspecified.

16. A boiler comprising a transverse bridge-wall, a member associatedwith one side of said wall and comprising a plurality of similarelements, each having a rearwardly inclined upper edge and jointlyforming a detlector coextensive in length with said member, means forseverally supporting-said elements in ond to end engagement upon saidbridge-wall and in spaced. relation thereto; the forward sides of saidelements forming an iinperforate wall serving as the rear wall of thefuel receptacle, and vertical ribs arranged upon each of said element-sserving to divide the space between the rear sides thereof and the -ontof said bridge-wall into a plurw Av of vt 'ti l.al passages forconducting secondary air to mingle with the products of combus Aon asthe same pass over the top of said bridge-wall, substantially asspecified.

17. il.. boiler comprising a fuel receptacle, a water-backed bridge-wallat the rear thereof, vertical. water-backed brackets on the front saidbridge-wall having recesses in the edges thereof, and stops on saidbrackets below said recesses, a plurality of plates arranged in end toend engagement and in spaced relation to said bridge-wall and forming`an i1nper"1 r:ite wall in front thereof; said plates each having arearwardly inclined upper edge and jointly forming a longitudinaldetlector coextensive in length with said bridge wall and each havinglugs adapted to be received by the recesses in the brackets of saidbridge-wall and to be supported upon the stops below the same whereby tohold said plates in position upon said bridge-wall, substantially asspecified.

18. A boiler comprising a fuel receptacle, a water-backed bridge-wall atthe rear thereof, vertical water-backed .supporting brackets extendingltherefrom, lateral flanges along the opposite longitudinal edges of saidsupporting brackets, said flanges having recesses in their edges, stopsupon the rear sides of said flanges below the recesses therein, aplurality of plates arranged in end to end engagement and in spacedrelation to said bridge-wall and forming at their front sides animperforate wall constituting the rear wall of said fuel receptacle;said plates each having a plurality of longitudinal ribs extending fromthe rear surface, and laterally extendinglugs on certain of said ribsadapted to be received by the recesses in said flanges and to be engagedby said stops whereby to hold said plates severally in position uponsaid bridgewall, substantially as specified.

Signed at the city of Buffalo, Erie County, State New York, this th dayof May, one thousand nine hundred and twenty-four.

FRANK B. HOV/*ELL

